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Exploring the Relationship Between Treatment and Causal Theory in Stuttering

Ann Packman, PhD Australian Stuttering Research Centre

ESFD, Antwerp, 2014

Overview

• Verbal communication and complexity theory
• “What causes stuttering?”

– causal models/theories – P&A 3-factor model

• Do our treatments for stuttering address cause?

Spoken language

• The most complex thing we humans do

– thinking up we want to say – constructing the language to say it – programming this into motor gestures (syllables) – 4-6 syllables per second, each one unique – all this, taking into account

• conversational partner
• topic
• purpose
• context

Verbal communication and complexity theory

Packman & Kuhn (ODC, 2008; IJSLP, 2009)

• Complexity theory/sciences

– nonlinear – initial condition and the “butterfly effect” – self-organising and dynamic

Communicative context Communicative environment

MIND BODY BRAIN

“What causes stuttering?”

• Many models and theories

– Systems control modeling

• Sensory Motor Modeling Theory
• Neuroscience Model
• Variability Model (Vmodel)

– Speech motor control

• Syllable Initiation Theory (SI Theory)
• Interhemispheric Interference Model

Models and theories (cont.)

– Cognitive and linguistic processing

• Neuropsycholinguistic Theory
• Covert Repair Hypothesis
• Suprasegmental Sentence Plan

Alignment Model

• EXPLAN

– Multifactorial

• Demands Capacities
• Dynamic Multifactorial Model

Let’s talk about cause

Packman & Attanasio (2004)

• Cause = necessary and sufficient conditions
• Individual instances of a phenomenon can

have triggers, e.g. bushfires

Rather than asking…

“What causes stuttering?”

we ask…

“What causes a moment of stuttering?”

The Packman & Attanasio (P&A) 3-factor causal model of moments of stuttering

Packman (ODC, 2011; JFD, 2012; Enfance, 2013)

• 1. Necessary

neural processing problem

• 2. Trigger

features of spoken language

• 3. Modulators

inherent to the individual

MODULATORS

• physiological arousal
• cognitive demands

TRIGGER

Inherent features of spoken language

• variable syllabic stress
• linguistic complexity

IMPAIRED NEURAL PROCESSING for spoken language

A MOMENT OF STUTTERING

P & A 3-factor model

FACTOR 1 Neural processing problem

• Functional

– Activations & deactivations

• Structural

– Volume – Diffusion Tensor Imaging (DTI)

Putting together the findings of recent imaging and genetic research

Cykowski et al. (NeuroImage, 2010)

Hypothesis:

The neural processing problem underlying stuttering is incomplete or late myelination of the white fibre tracts subserving the production of spoken language

FACTOR 2 Variability of syllabic stress

Packman et al. (CLP,1996)

“Buy Bobby a puppy” “You buy Bobby a puppy now if he wants one”

FACTOR 2: Effects of linguistic complexity on motor stability

see Smith and colleagues ( JSLHR, 2000)

FACTOR 3 Modulators

Alm (JFD, in press), Eggers et al. (JFD, 2013), Jones et al. (JCD, 2014), Metten et al. (Dis. Rehab., 2011)

• Determine the triggering threshold

– physiological arousal

• Anxiety? Excitement? Temperament?
• influenced by environment

– cognitive demands

• multi-tasking

• Explanatory power?

Stuttering not normal disfluency Onset and development Topography Natural recovery Variability

• Testability?
• Parsimony?
• Heuristic value?

Evaluating the P&A 3-Factor Model

MODULATING FACTORS

• physiological arousal
• cognitive demands

A MOMENT OF STUTTERING

TRIGGER

Inherent features of spoken language

• variable syllabic stress
• linguistic complexity

IMPAIRED NEURAL PROCESSING for spoken language

Behavioral treatments designed to reduce stuttering DIRECT INDIRECT Other treatments PSYCHOLOGICAL (incl. CBT) PHARMACEUTICAL

Do our treatments for stuttering address cause?

Theory and therapy

Should theory drive therapy? Can therapy drive theory?

Thank you! Dankjewel!

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• n causality. Journal of Fluency Disorders. In Press.

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